In recent years, organic EL devices have been under intensive investigation. One organic EL device basically comprises a hole injecting electrode, a thin film formed on the hole injecting electrode by evaporating a hole transporting material such as triphenyldiamine (TPD), a light emitting layer of a fluorescent material such as an aluminum quinolinol complex (Alq.sup.3) laminated on the hole transporting thin film, and a metal electrode (an electron injecting electrode) formed thereon from a metal having a low work function such as magnesium or Mg. This organic EL device attracts attentions because it can achieve a very high luminance ranging from several hundreds to tens of thousands cd/m.sup.2 with a voltage of approximately 10 volts.
In a typical process of providing such an organic EL display in a film form, for instance, an ITO transparent electrode in a film form is first provided. Then, only light emitting portions are exposed from the ITO transparent electrode while the rest thereof is covered with an insulating layer. Finally, organic layers and electron injecting electrodes, each in a film form, are provided on the transparent electrode so that a given light emitting pattern can be obtained. In this case, while the electron injecting electrodes serve as common electrodes, a given voltage is applied between each ITO transparent electrode providing a light emitting portion and the associated electron injecting electrode, so that the desired light emitting portion can give out light. Consequently, it is preferable that the electron injecting electrodes providing common electrodes and organic layers connected thereto are isolated for each segment group, each data line (scanning line) or the like, so that they can be independently driven. To this end, various means for element isolation have so far been developed in the art.
An element-isolating structure set forth in JP-A-9-330792 (as spacer, and overhang members) is known for the element-isolating means. This element-isolating structure is obtained by providing an insulating layer on a hole injecting electrode according to a film pattern, forming a spacer layer such as a polyimide layer thereon, coating a positive resist material on the spacer layer to form a photo-pattern for element isolation, and developing the photo-pattern for removal of unexposed portions and the spacer layer underneath them. Details of this element-isolating structure are disclosed in the specification, and so are no longer described.
When the organic EL device is exposed to the outside air, on the other hand, the electrodes oxidize while the organic layers degrade due to moisture. For this reason, it is required to use a structure in which they are airtightly confined to shield them from the outside air, for instance, by providing a protective or sealing film after the provision of the electron injecting electrode or providing a sealing plate on the side of the electron injecting electrode that is not opposite to the substrate. Among these, the sealing plate is particularly effective for protecting the organic layers against mechanical external force, and so can be a structural member indispensable for displays. If the sealing plate is pressed on the peripheral portion of the substrate where a spacer higher than laminated organic EL device structures such as organic layers and electron injection electrode, and an adhesive agent serving as a sealing material have been provided, the sealing plate can then be located at a position spaced away from the substrate by the height of the spacer, i.e., at a position that does not interfere with the organic EL structures such as organic layers and electron injecting electrode.
In most cases, however, a glass or synthetic resin plate actually used as the sealing plate is uneven in thickness or irregular in surface shape, or is otherwise distorted. Even though the sealing plate is located at an end position higher than the organic EL structures, the organic EL device structures often interfere with the sealing plate due to a distortion of the sealing plate, etc., resulting in damage to, and a breakdown of, the organic EL device structures. Such interference with the sealing plate may be avoided by imparting an adequate height to the spacer. If a spacer usually formed by means of photolithography is too thick, however, it will then have an adverse influence on the photolithographic step to be carried out after the provision of the spacer, resulting in a distortion of other pattern configuration located in the vicinity of the spacer. That is, when it is necessary to carry out the photolithographic step subsequently to the provision of the spacer, the thickness of the spacer provided prior to the photolithographic step is limited to approximately 10 .mu.m. Thus, the spacer-incorporating step should be carried out after the provision of the element-isolating structure.
A printing process of forming a polyimide or other resin film of, e.g., 20 to 50 .mu.m in thickness is suitable for the provision of a thick spacer. However, a problem inherent in the printing process is that exposed portions of the surface of the electrode on which organic films are to be provided are susceptible to contamination, often resulting in defects such as light emission variations.
A material for forming a thick resist of about 20 to 50 .mu.m in one coating operation by means of photolithograpy, on the other hand, is known in the art. In order for the formation of a thick resist to have no influence on the element-isolating structure, however, the material to be selected for the element-isolating structure is under severe limitations. In either case, some considerable expense incurs due to the need of an additional step.